市售婴幼儿米粉中克罗诺杆菌的分子分型和耐药分析

为了解婴幼儿配方米粉中克罗诺杆菌的污染情况、分子分型特征及耐药性情况，采集广西区内市售6个厂家和品牌不同配方的婴幼儿米粉进行克罗诺杆菌分离及fusA基因的扩增、测序和MLST数据库比对分析。并应用脉冲场凝胶电泳（PFGE）对菌株进行分型鉴定及微量肉汤稀释法测定分离株对8种常见抗生素的最小抑菌浓度（Minimal Inhibitory Concentrations，MICs）。采集的268份婴幼儿米粉共分离到32株克罗诺杆菌，检出率为11.94%，菌株鉴定结果显示32株分离株包括22株C.sakazakii、6株C.malonaticus、3株C.dublinensis和1株C.muytjensii。不同添加成分的婴幼儿配方米粉污染情况差异明显，其中添加淮莲和果蔬的米粉污染率最高为17.78%和15.38%。PFGE分析显示32个菌株共分成32种不同的分子型，相似度为61.20%~92.30%，所有分离株对环丙沙星、庆大霉素和头孢噻肟都敏感，部分菌株（6.25%~43.75%）对氯霉素、四环素、甲氧苄啶/磺胺甲基异恶唑、头孢西丁和萘啶酸表现为中等敏感，有2个菌株对氯霉素表现为抗性。结果表明市售婴幼儿配方米粉中存在一定的克罗诺杆菌污染，尤其是添加营养成分的米粉。婴幼儿配方米粉中克罗诺杆菌污染来源广泛，部分菌株对一些抗菌药表现为中等敏感甚至是抗性，提示克罗诺杆菌对抗菌药的敏感性呈现减弱的趋势。

Molecular Typing and Drug Resistance of Cronobacter spp. in Commercial Formula Rice Flour Products for Infants and Young Children

To understand the contamination, molecular typing and drug resistance of Cronobacter spp. in formula rice flour products for infants and young children, the formula products from six different manufacturers and brands with different ingredients were collected in the markets of Guangxi city for isolation of Kronobacter, and fusA gene amplification, sequencing and MLST database comparative analysis. The molecular typing of the isolates was detected by pulsed field gel electrophoresis (PFGE), and the minimal inhibitory concentration (Minimal Inhibitory Concentrations, MICs) of the isolates against 8 common antibiotics was analyzed by the broth microdilution method. Two hundred sixty-eight samples of formula rice flour products were collected and 32 strains of Cronobacter spp. were isolated, with the detection rate as 11.94%. The strain identification results showed 32 isolated strains, including 22 strains of C. sakazakii, 6 strains of C. malonaticus, 3 strains of C. dublinensis and 1 strain of C. muytjensii. The contamination of the formula rice flour products with different ingredients differed significantly, with those ingredients fortified with Huailian or fruits and vegetable having the highest contamination rates (17.78% and 15.38%, respectively). PFGE analysis showed that 32 strains were divided into 32 different molecular types, with the similarity in the range of 61.20%~92.30%. All the isolates were sensitive to ciprofloxacin, gentamycin and cefotaxime, with some (6.25%~43.75%) being moderately sensitive to chloramphenicol,tetracycline, trimethoprim/sulfamethoxazole, cefoxitin and nalidixic acid, and two being resistant to chloramphenicol. The results showed a certain degree of contamination of Cronobacter spp. in the formula rice flour products, especially those fortified with nutrients. The source of contaminated Cronobacter spp. is broad, with some strains from the formula rice flour products being moderately sensitive or even resistant to some antibiotics, indicating that the sensitivity of Cronobacter spp. to antibiotics was on a weakening trend.